> So now, rather than "dt" being a definition term, it's become, well I
> don't know what it's become. Something.
Item Header, or possibly Item Label.
That is arguably a better name for even traditional uses (other than
glossaries).
Of course "dt" is a horrible way to spell that. It may still be the
lesser of evils, compared to inventing yet more special case
small-scale headers, and leaving <dt> as effectively "the shorter half
of a list item, mostly".
-jJ